JP6704240B2 - Classifier - Google Patents

Description

The present invention relates to a classifying device for classifying a raw material powder into a fine powder and a coarse powder, and in particular, classification is performed by using a swirling flow caused by rotation of a classification rotor to obtain a product having a predetermined particle size range. Related to the classifier.

Toners used in copiers, printers, etc., which have become widespread in recent years, are pulverized by a (fine) pulverizer and powder of several μm order containing various particle diameters, It is manufactured by classifying powder. Therefore, it is required to classify fine powder finer than a predetermined particle diameter with high accuracy.

Conventionally, as such a powder classifying device, an airflow rotary classifying device for classifying fine powder and coarse powder by using a swirling flow caused by rotation of a classifying rotor has been widely used, and the classification principle will be briefly described. Then, it is as follows.

In the classification space, the powder is placed on the air flow from the outside to the inside, and further, the air flow is swung in the direction of rotation of the axis perpendicular to the direction of the air flow centered on the inside. The swirling action exerts an outward centrifugal force and an inward centripetal force due to the air flow, and the larger the particle size, the greater the centrifugal force. The powder tends to collect on the inner peripheral side.

Therefore, if the airflow is discharged from both the outer peripheral portion and the central portion, the airflow discharged from the outer peripheral portion contains a large amount of powder (coarse powder) having a large particle diameter, and the airflow discharged from the central portion has a particle diameter of It contains a lot of small powder (fine powder). From this, the raw material powder in which powders of various sizes are mixed is classified into coarse powder and fine powder.

Such an air current rotary type classifying device is described in, for example, Patent Documents 1 to 4.

JP, 2010-253394, A JP 7-236861 A JP, 2006-35031, A Utility model registration No. 3015458

However, according to the above-mentioned principle, the air flow rotary classifier discharges powder from the outer peripheral part in the classifying space because the ratio of the powder having a large particle diameter gradually increases from the inner peripheral side to the outer peripheral side. It is difficult to completely separate the powder contained in the generated airflow and the powder contained in the airflow discharged from the inner peripheral portion into particles having a predetermined particle size.

For this reason, for example, when manufacturing high-quality powder such as toner, it is difficult to remove fine fine powder with high accuracy and to adjust the classification point by an airflow rotary classification device.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is possible to enhance the classification accuracy with a simple and small configuration, and a classification device that can easily adjust the classification points. The purpose is to provide.

In order to solve the above problems, a first aspect of the present invention is a classifying device for classifying a raw material powder into fine powder particles and coarse powder particles, which is provided inside a casing and the casing. A rotatable classifying rotor, and an air introducing section arranged below the classifying rotor and arranged on an outer peripheral portion of the casing for supplying air for blowing up a part of the raw material powder upward, The air introducing portion has an air inlet for allowing the air to flow into the casing on an inner peripheral portion thereof, and a throttle for narrowing a flow passage cross-sectional area of the air on an inner peripheral side of the air inlet. It has a mechanism.

According to a second aspect of the present invention, in the first aspect, the throttle mechanism is provided with an annular body at an upper portion on an inner peripheral side of the air inlet, and the air is below the annular body of the air inlet. Further, it is configured so as to pass through the throttle mechanism and flow into the classification rotor.

A third aspect of the present invention is characterized in that, in the second aspect, the annular body has a substantially cylindrical shape.

A fourth aspect of the present invention is characterized in that, in the second aspect, the annular body has, on its inner peripheral side, an inverted conical surface which is tapered downward.

In a fifth aspect of the present invention according to the fourth aspect, an inclination angle of the inverted conical surface of the annular body is an inclination angle of an inner peripheral surface of the casing at a portion above the air introducing portion of the casing. Is substantially the same as the above.

A sixth aspect of the present invention is characterized in that, in any of the second to fifth aspects, the annular body is detachably attached to the air introducing portion.

According to the present invention, it is possible to provide an airflow rotary classifying device that can improve the classification accuracy with a simple and small structure and that can easily adjust the classification point.

1 is a vertical cross-sectional view schematically showing a classification device according to an embodiment of the present invention. FIG. 2 is a vertical cross-sectional view showing the shapes of various annular bodies used in the classification device shown in FIG. 1. The figure which showed distribution of the particle|grains of 5 micrometers or less in the powder after a classification process. The figure which showed the relationship between the 50% particle diameter (d50) and the number of particles of 3 micrometers or less in the powder after a classification process. The figure which showed the relationship of the ratio of the particle of 4 micrometers or less and the particle of 3 micrometers or less in the powder after a classification process. The figure which showed the relationship of the ratio of the particle of 4 micrometers or less and the particle of 2.5 micrometers or less in the powder after a classification process. The figure which showed the particle|grains of 4 micrometers or less in the powder after a classification process, and the relationship of a yield. The longitudinal cross-sectional view which showed typically the classification device by other embodiment of this invention.

Hereinafter, a classification device according to an embodiment of the present invention will be described with reference to FIGS. 1 to 4.

The classification device according to the present embodiment includes a cylindrical casing 1, and a rotatable classification rotor 2 that forms a classification space 9 (9a, 9b) is provided inside the casing 1.

The classification rotor 2 is provided at the center of the casing 1 and is rotated by a rotating shaft 3 extending in the vertical direction. The rotating shaft 3 is rotationally driven by an electric motor (not shown) via a gear mechanism, a pulley mechanism or other power transmission mechanism (not shown).

The classification rotor 2 has an annular classification space 9 formed in the inner peripheral portion thereof, and a plurality of blades 8 arranged at equal intervals in the outer peripheral portion thereof. When the classification rotor 2 is rotated, the air inside the classification space 9 is swirled, and a swirling flow is generated.

A raw material powder supply port 6 for supplying the raw material powder 11 into the casing 1 is provided in the upper part of the casing 1, and the raw material powder 11 is a raw material powder connected to the raw material powder supply port 6. It is introduced into the casing 1 by the carrier air from the body supply pipe 7.

A primary air introducing portion 4 for supplying primary air toward the classification rotor 2 is provided on the outer peripheral portion of the casing 1 on the side of the classification rotor 2 over the entire circumference. The primary air introduction part 4 includes a primary air intake 17 for introducing the primary air into the casing 1. A plurality of guide vanes 5 are arranged in the inner peripheral region of the primary air introducing portion 4. The guide vanes 5 are arranged so that the swirling flow generated by the rotation of the classification rotor 2 allows the air to smoothly flow into the casing 1 from the primary air introducing portion 4.

Since the primary air introduction part 4 is formed over the entire circumference of the outer peripheral part of the casing 1, the raw material powder 11 introduced from the raw material powder supply port 6 is swirled by the rotation of the primary air and the classification rotor 2. By the flow, the outer peripheral portion of the classification rotor 2 can be made almost uniform or dispersed and flow into the classification space 9.

The raw material powder 11 that has flowed into the classifying space 9 swirls in the classifying space 9 by a swirling flow, and coarse powder particles are collected on the outer peripheral side by centrifugal force, and fine powder particles are collected on the inner peripheral side. That is, in the concentration distribution of the particle diameter of the raw material powder 11 in the radial direction of the classification space 9, the concentration of fine powder is high toward the center and the concentration of coarse powder is high toward the outer peripheral portion.

An air flow discharge mechanism (not shown) for discharging an air flow containing fine powder to the outside is provided at the center of the classification rotor 2, and the fine powder smaller than a predetermined particle diameter moved to the inner peripheral side of the classification space 9 is provided. Is collected to the outside via the air flow discharge mechanism by the fine powder recovery pipe 10 connected to the air flow discharge mechanism. The agglomerates of coarse powder and fine powder that have moved to the outer peripheral side by the centrifugal force are discharged outward from the outer peripheral portion of the classification rotor 2 and fall downward.

In addition, in the present embodiment, in order to improve the classification accuracy, the classification rotors 2 are provided in upper and lower two stages, and the coarse powder discharged outward from the upper classification rotor 2a having the upper classification space 9a. The agglomerates of fine powder, and the raw material powder 11 that was introduced from the raw material powder supply port 6 but dropped without flowing into the upper classifying rotor 2 were (re)removed to the lower classifying rotor 2b during the fall. Inflow.

The raw material powder 11 that has flowed into the lower classification rotor 2b, that is, the lower classification space 9b, is classified into fine powder and coarse powder by the same action as the upper classification rotor 2a, and the fine powder is distributed to the center of the classification rotor 2b. The raw material powder 11 having a larger particle size than the predetermined particle diameter, which is recovered to the outside by the fine powder recovery pipe connected to the airflow exhausting mechanism through the provided airflow exhausting mechanism (not shown) and is moved outward by the centrifugal force, , Is discharged outward from the outer peripheral portion of the classification rotor 2b and falls below the casing 1.

As described above, in the classifying device according to the present embodiment, the classifying rotor 2 is provided in the upper and lower two stages, but the structure of the classifying rotor is not limited to the upper and lower two stages, and may be a single stage structure.

Below the primary air introduction part 4 of the casing 1, a secondary air introduction part 21 having a secondary air intake 22 is provided. The secondary air introducing section 21 corresponds to the air introducing section in the present invention. Further, the secondary air introducing portion 21 is provided with a secondary air inlet 23 for allowing the secondary air to flow into the casing 1 in the inner peripheral portion thereof, and the secondary air inlet 23 has a circumference or the like. It is provided with a plurality of guide vanes 24 arranged at intervals. The guide vanes 24 are inclined in the horizontal direction in the radial direction so that the secondary air flowing into the casing 1 forms a swirling flow.

The secondary air that has flowed into the casing 1 from the secondary air inlet 23 is the raw material powder 11 that has been introduced from the raw material powder supply port 6 and has dropped without reaching the blade 8 of the classification rotor 2. , And particles (coarse particles and aggregates) that have been classified by the classification rotor 2 and discharged from the outer peripheral portion of the classification rotor 2 and have fallen are raised while swirling in the casing 1. In this way, the aggregates are disentangled when riding on the secondary air, and flow into the classifying rotor 2 again together with the coarse powder, and undergo the classifying action again. Coarse powder and agglomerates that do not rise in the secondary air and are further loosened in some cases and then discharged to the product side.

The inclination direction of the guide vanes 24 is a direction in which a swirling flow is generated in the same direction as the swirling flow direction of the primary air generated by the blade 8 of the classification rotor 2. As a result, the raw material powder 11 and the like pushed back upward by the secondary air can smoothly flow into the classification rotor 2 along with the swirling and rising secondary air.

In the classification device according to the present embodiment, the throttle mechanism 25 that narrows the flow passage cross-sectional area of the secondary air is provided on the inner peripheral side of the guide vane 24 of the secondary air inlet 23. The throttling mechanism 25 is provided with an annular body 26 at an upper portion on the inner peripheral side of the secondary air inlet 23, and the secondary air passes through the throttling mechanism 25 from below the annular body 26 of the secondary air inlet 23 to perform classification. It is configured to flow into the rotor 2.

By thus providing the throttle mechanism 25 and narrowing the flow passage cross-sectional area of the secondary air at the secondary air inlet 23, the flow velocity of the inflowing air from the secondary air inlet 23 is increased, so that the swirl velocity is increased. As a result, the effect of blowing up the raw material powder 11 and the like is improved.

Further, the throttle mechanism 25 projects its lower portion to the inner peripheral side to narrow the flow passage cross-sectional area for the rise of the secondary air that has flowed in from the secondary air inlet 23. It is preferable to increase the flow velocity by the throttling effect (see FIG. 1). As a result, the effect of blowing up the falling raw material powder 11 and the like can be improved.

In this case, as shown in FIG. 1, it is preferable that the diaphragm mechanism 25 further has an inverted frustoconical inner peripheral surface with the inner peripheral side inclined from the upper end of the outer peripheral portion. As a result, the raw material powder 11 that has fallen inside the casing 1 can slide down without accumulating on the upper surface or the inner peripheral surface of the throttle mechanism 25, and the raw material powder 11 that has slid down can be moved upward. Can be blown up by air.

Considering that the inclination of the reverse conical surface which is the inner peripheral surface of the throttle mechanism 25 minimizes the influence on the rise of the secondary air and the fall of the raw material powder 11, the casing 1 above the throttle mechanism 25 is also considered. It is preferable that the inclination of the inner surface is substantially the same.

When the fine powder removal performance is improved by providing the squeezing mechanism 25, the proportion of the fine powder contained in the recovered coarse powder decreases, and as a result, the coarse powder as a product is reduced. The classification points will increase. For example, when the classification point is evaluated by 50% particle diameter d50, the fine powder is reduced, and the particle diameter corresponding to the ratio of 50% by integrating from the smaller particle diameter in the integrated particle size distribution shifts to the coarse powder side. Because it will be. Here, the 50% particle diameter d50 means the particle diameter at which the cumulative volume ratio becomes 50% in the particle size distribution of the powder.

In the case of the squeezing mechanism 25 having a high performance of removing fine particles, the classification point may be increased more than necessary. In this regard, according to the present embodiment, in relation to the target powder product, in the allowable range of the fine powder removal rate, by selecting and using the throttling mechanism 25 corresponding to a predetermined classification point, The classification point can be adjusted.

That is, in the present embodiment, the annular body 26 that constitutes the diaphragm mechanism 25 has a detachable structure, and the annular body 26 corresponding to a predetermined classification point is appropriately exchanged for use.

As a conventional classification point adjusting means, adjustment of the gap of the guide vane 24 of the secondary air inlet 23 was sometimes performed. However, since the gap adjustment was a precision work in 0.1 mm units, the entire guide The work of accurately setting the gap between the blades 24 has problems such as requiring a high degree of skill and a great deal of labor (for example, refer to Patent Document 4).

On the other hand, in the present embodiment, since the classification point can be adjusted by appropriately exchanging and using the annular body 26 corresponding to the predetermined classification point, it is necessary to have skill in adjusting the classification point. Instead, it is possible to adjust the classification points very simply.

As shown in FIG. 1, the annular body 26 is attached to the secondary air introducing portion 21 by forming a flange-shaped protrusion 27 protruding outward on the outer peripheral portion of the upper portion of the annular body 26 in the secondary air introducing portion 21. This is done by fitting it in the recess 28.

<Various Examples>
In order to confirm the effects such as the classification accuracy by the diaphragm mechanism 25, the results of the test according to the embodiment using four kinds of annular bodies 26 having different shapes as the diaphragm mechanism 25 will be described below.

(1) Classifier used: Fine powder classifier EFS10 made by Earth Technica [Specification of secondary air inlet 23]
Height: about 130 mm
Inner surface diameter: about 430mm

(2) Test conditions Raw material powder: 50% particle diameter d50: about 6.7 μm
Air volume: Secondary air flow rate 18Nm ³ /min (total air volume of about 21Nm ³ /min)

(3) Example of annular body 26
(i) Example 1 (type ax)
The first embodiment of the annular body 26 has a substantially cylindrical shape with a height of 55 mm, as shown in FIG. Hereinafter, the annular body 26 of the first embodiment will be referred to as a type ax.

A collar-shaped protrusion 27 for fitting into the recess 28 of the secondary air introduction portion 21 is formed on the outer peripheral portion of the upper portion of the annular body 26 (the same applies to the annular bodies in other embodiments).

In Example 1, the lower portion (bottom portion) of the annular body 26 is not provided with the protrusion to the inner peripheral side, but at the secondary air inlet 23, the flow path of the secondary air flowing into the casing 1 is narrowed. As a result, the effect of blowing up the raw material powder 11 due to the increase in the flow velocity can be expected.

In the first embodiment, the secondary air inlet 23 is narrowed down to about 58% of the flow passage cross-sectional area before the annular body 26 is provided.

(ii) Example 2 (type ay)
As shown in FIG. 2B, the second embodiment of the annular body 26 has a substantially cylindrical outer shape as in the first embodiment, but the height is as high as 80 mm. Hereinafter, the annular body 26 of the second embodiment will be referred to as type ay.

In the second embodiment, the secondary air inlet 23 has a large reduction of about 38% of the flow passage cross-sectional area before the annular body 26 is provided. By comparing with the first embodiment, the inner peripheral side This is to confirm the effect of narrowing the inflow air flow path to.

(iii) Example 3 (type bx)
In Example 3 of the annular body 26, as shown in FIG. 2(3), the height is 55 mm (same as type ax), the inner peripheral surface is an inverted conical surface having an inclination, and the lower part (bottom part) is It has an overhanging shape. The inclination angle of the inverted conical surface is approximately the same as the inclination of the inner surface of the casing 1 above the diaphragm mechanism 25, and is about 38 degrees. Hereinafter, the annular body 26 of the third embodiment will be referred to as type bx.

By comparing with Example 1, it is possible to confirm the effect of narrowing down the secondary air rising flow.

In the third embodiment, as in the first embodiment, the secondary air inlet 23 is narrowed down to about 58%. As for the ascending flow, the diameter is narrowed down from 430 mm to 340 mm (about 79%) (about 63% in area).

(iv) Example 4 (type by)
In Example 4 of the annular body 26, as shown in FIG. 2(4), the height is 80 mm (same as type ay), the inner peripheral surface is an inverted conical surface with an inclination, and the lower part (bottom part) is It has an overhanging shape. The inclination angle of the inverted conical surface is approximately the same as the inclination of the inner surface of the casing 1 above the diaphragm mechanism 25, and is about 38 degrees. Hereinafter, the annular body 26 of the fourth embodiment will be referred to as type by.

In the fourth embodiment, as in the second embodiment, the secondary air inlet 23 is narrowed down to about 38%. The upward flow is narrowed down from 430 mm to 300 mm (about 70%) in diameter (about 49% in area).

(4) Confirmation of effect by test The results of the confirmation test of classification performance and the like performed in five cases including the case where the annular body 26 is not provided as a comparative example in the example using the four types of annular bodies 26 are shown. This will be described below.

(i) Distribution of Particles of 5 μm or Less FIG. 3 is a diagram showing the number distribution (integration) of fine powder having a particle diameter of 5 μm or less contained in the coarse powder which is classified and recovered.

From FIG. 3, it can be seen that the ratio of fine powder is reduced, the classification accuracy is improved, and the throttling mechanism is effective in any of the examples as compared with the case without the annular body (comparative example).

The decrease in the proportion of fine powder in the examples is particularly remarkable in the region where the particle diameter is small, and it is found that bx and by are excellent for the fine powder of 3.5 μm or less (the proportions are almost the same). It should be noted that there is no difference between ax and ay, which are annular bodies having a substantially cylindrical shape, because they are almost overlapped with each other. From this, it is understood that the narrowing down to the upward airflow rather than the narrowing down from the secondary air inlet 23 to the inner circumferential side is particularly effective in improving the classification accuracy as the particles become finer.

As can be seen from FIG. 3, the ratio of the fine powder contained in the coarse powder powder classified and collected differs depending on the type of the annular body 26, and, for example, d50 is the direction in which the particle diameter is large in accordance with the ratio. Shift to. This indicates that, as described above, in the present embodiment, the classification point can be adjusted by appropriately exchanging the annular bodies 26 of different types.

(ii) Relationship between 50% particle diameter (d50) and number of particles of 3 μm or less FIG. 4 is a diagram showing the number ratio of fine particles of 3 μm or less to 50% particle diameter (d50) of classified coarse powder. Therefore, it can be said that the smaller the proportion of the fine powder of 3 μm or less, the more the fine powder of 3 μm or less is excluded, and the higher the classification accuracy.

As can be seen from FIG. 4, as compared with the case without the annular body (comparative example), by providing the throttling mechanism 25 as described above, the fine powder ratio of 3 μm or less is remarkably reduced, that is, the classification accuracy is improved. , Bx shows excellent classification accuracy.

(iii) Relationship between the ratio of particles of 4 μm or less and particles of 3 μm or less FIG. 5 is a diagram showing the relationship of the ratio of particles of 4 μm or less and particles of 3 μm or less contained in the classified coarse powder. It can be said that the smaller the proportion of particles having a particle diameter of 3 μm or less, the higher the classification accuracy.

Also in FIG. 5, the classification accuracy is remarkably improved by providing the annular body 26, that is, the diaphragm mechanism 25 as described above, as compared with the comparative example (without the annular body), and particularly the classification accuracy is excellent in by and bx. You can see that

(iv) Relationship between Ratio of Particles of 4 μm or Less and Particles of 2.5 μm or Less FIG. 6 shows particles of 4 μm or less contained in classified coarse powder, and particles of 2.5 μm or less, which are particularly fine powders. It is a diagram showing the relationship of the proportion of particles, and it can be said that the smaller the proportion of particles having a particle diameter of 2.5 μm or less, the higher the classification accuracy in fine fine powder.

As can be seen from FIG. 6, as compared with the case without the annular body (comparative example), by providing the annular body 26 as described above, the classification accuracy is remarkably improved, and particularly by and bx are excellent in the classification accuracy. I understand.

(v) Relationship between Particles of 4 μm or Less and Yield FIG. 7 is a diagram showing the relationship between the number ratio of particles of 4 μm or less contained in the classified coarse powder and the yield.

As can be seen from FIG. 7, in each of the examples, the yield is remarkably improved as compared with the case without the ring-shaped body (comparative example).

From the above test data, it is shown that the classification accuracy and the yield are remarkably improved by providing the annular body 26, that is, the throttling mechanism 25 at the secondary air inlet 23. Moreover, since the classification accuracy and the yield are excellent in by and bx as the type of the annular body 26, not only the flow path from the secondary air inlet 23 to the inner peripheral side but also the flow path for the upward flow It can be seen that also has the effect of diaphragm.

As described above, according to this embodiment, the following effects can be realized.
(i) By providing the throttle mechanism at the secondary air inlet, the classification accuracy can be improved with a simple and small structure.
(ii) The classification point can be easily adjusted by appropriately exchanging and using the diaphragm mechanism corresponding to the classification point.

Next, another embodiment of the present invention will be described with reference to FIG. The same parts as those in the above-described embodiment are designated by the same reference numerals and the description thereof will be omitted below.

As shown in FIG. 8, the classification device according to the present embodiment has the configuration of the above-described embodiment (FIG. 1) in which the primary air introducing portion 4 provided on the outer peripheral portion of the casing 1 is deleted.

Even in the classifying device that does not include the primary air introducing part as in the present embodiment, since the force (centripetal force) toward the discharge direction is exerted by the suction of the exhaust fan downstream of the classifying device, this centripetal force causes the raw material powder. Flows into the classification space 9.

Then, even in the classifying device of the present embodiment that does not include the primary air introducing portion, the above-described excellent effect of the diaphragm mechanism 25 can be achieved.

1 Casing 2 Classifying rotor 2a Upper classifying rotor 2b Lower classifying rotor 3 Rotating shaft 4 Primary air inlet 5 Guide vane 6 Raw material powder supply port 7 Raw material powder supply pipe 8 Blade 9 Classifying space 9a Upper classifying space 9b Lower stage Classification space 10 Fine powder recovery pipe 11 Raw material powder 17 Primary air inlet 21 Secondary air inlet 22 Secondary air inlet 23 Secondary air inlet 24 Guide vane 25 Throttling mechanism 26 Annular body 27 Collar-like protrusion 28 Recess

Claims (4)

A classification device for classifying raw material powder into fine powder particles and coarse powder particles,
A casing,
A rotatable classification rotor provided inside the casing,
An air introduction unit that is arranged below the classification rotor and on an outer peripheral portion of the casing, and supplies air for blowing a part of the raw material powder upward,
The air introduction part has an air inlet on its inner peripheral part for allowing the air to flow into the casing,
Have a diaphragm mechanism for narrowing the flow path cross-sectional area of the air in the air inlet,
The throttling mechanism has an annular body detachably provided in the air introducing portion so as to close a part of the upper side of the air inlet, and the air is more than the annular body of the air inlet. A classifying device configured to be introduced from a lower portion, pass through the throttling mechanism, and flow into the classifying rotor . It said annular body, and has a circular cylindrical shape, classification apparatus according to claim 1. The classifying device according to claim 1 , wherein the annular body has an inverted conical surface on the inner peripheral side thereof, which is tapered downward. Wherein the inclination angle of the reverse conical surface of the annular body, wherein the inclination angle and the same of the inner peripheral surface of the casing of the upper part than air introduction part of the casing, the classification apparatus according to claim 3.

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